Grinding apparatus



Sept. 16, 1969 A. J. A. ASPLUND ETAL 3,457,323

GRINDING APPARATUS Filed Sept. 22, 1965 5 Sheets-Sheet 1 Fig.1

Sept. 16, 1969 U ETAL 3,467,323

GRINDING APPARATUS Filed Sept. 22, 1965 5 Sheets-Sheet 2 Fig.2

Sepf. 16, i969 sp u p ET AL 3,467,323

GRINDING APPARATUS Filed Sept. 22, 1965 5 Sheets-Sheet 4.

Fig.1.

AnmJoA Ari/0r ASPluna? k J nan Gunner lhj, Johansson By 711W Sept. 16, 1969 Q AsPLUND ETAL 3,457,323

GRINDING APPARATUS Filed Sept. 22, 1965 5 Sheets-Sheet s Ame, /o loam AH/wr A?! "J United States Patent 3,467,323 GRINDING APPARATUS Arne Johan Arthur Asplund, Lidingo, and Johan Gunnar Inge Johansson, N asbypark, Sweden, assignors to Defibrator Aktiebolag, Stockholm, Sweden, 21 corporation of Sweden Filed Sept. 22, 1965, Ser. No. 489,233 Claims priority, application Sweden, Sept. 25, 1964, 11,571/64 Int. Cl. B02c 23/ 02 U.S. Cl. 241247 6 Claims ABSTRACT OF THE DISCLOSURE A grinding apparatus for vegetable material particularly adapted for the grinding of relatively large pieces of the material, the apparatus including a pair of grinding discs between which the material is fed. The discs are carried on shafts and at least one of the discs is rotated. A conveyor is arranged concentrically around one of the shafts for feeding the material between the discs and the conveyor is rotated at a lower speed than the speed of rotation of the rotated disc.

This invention relates to a grinding apparatus for vegetable material, especially in relatively large pieces.

More particularly this invention relates to a grinding apparatus for vegetable material, especially in relatively large pieces, comprising two grinding discs rotatable in relationship to one aonther and displaceable in axial direction relatively to one another by means of a servomotor, the goods to be ground being fed between the grinding surfaces of said discs by means of a rotatable conveyor provided with entrainers. The invention has primarily come into existence in connection with the development of a method according to which the vegetable material in the form of chips or other relatively large pieces is directly ground to pulp which means without being exposed to a steam atmosphere or a cooking step. The grinding may in this connection be conducted in three steps of which at least the first step is carried out with a grinding apparatus according to the invention. It has proved in this connection that the feeding of the chips involves particular difficulties with conventional apparatus in particular because the chips cannot be dispersed in water and therefore show great tendency of forming plugs which has a highly obstructing effect on the grinding work.

One main object of the invention is to provide a grinding apparatus of the type in consideration the structure of which avoids said inconvenience. According to one main feature of the invention the conveyor is disposed to be rotated with a substantially lower speed than the rotatable grinding disc and is located in an annular interspace surrounding the shaft of said disc.

The invention is especially of importance for apparatus the two grinding discs of which are carried by rotatable shafts with the conveyor concentrically enclosing one of said shafts.

Further objects and advantages of the invention will become apparent from the following description, considered in connection with the accompanying drawings which form part of this specification and of which:

FIG. 1 is a lateral projection of a grinding apparatus constructed according to the invention.

FIGS. 2 to 4 are vertical longitudinal sections through the apparatus taken subsequently one after the other so that each of them comprises one of the sections A, B and C, respectively, of FIG. 1.

FIG. 5 is a partially longitudinal section of a portion 3,467,323 Patented Sept. 16, 1969 of the conveyor according to a modified embodiment of the invention.

FIG. 6 finally is an end view of the conveyor according to FIG. 5.

Referring to the drawings, reference numeral 10 denotes the frame of the apparatus in which two shafts 12, 14 are mounted coaxially and rotated each by its motor 16 and 18, respectively. The shaft 12 is carried by a radial thrust bearing 20 and a combined radial and axial thrust bearing 22, the stationary outer rings respectively 21, 23 of said bearings in turn being located in a piston 26 of a servo-motor 24 which piston concentrically surrounds the shaft 12, but does not rotate with the same. Provided on the free end of the shaft 12 is a grinding disc 28. The other shaft 14 is mounted in the frame 10* by means of a combined radial and axial thrust bearing 30 and is further supported by a radial thrust bearing 32. Secured onto the free end of the shaft 14 is a grinding disc 34 which together with the grinding disc 28 is enclosed by a base open casing 36. The two grinding discs are in known manner provided with segments 38 forming against one another grinding surfaces 40. The shaft 12 is axially displaceable together with the piston 26 whereas the shaft 14 is blocked in axial direction relatively to the frame by the bearing 30.

The piston 26 of the servo-motor is on its outside provided with an annular flange 42 and is with sealing sliding fit axially movable within a chamber 44 formed in the stationary housing 46 of the servo-motor. The chamber 44 has at its both ends inlets and outlets 48, 50 for a liquid under pressure such as oil. When pressure medium is supplied through the conduit 48 the piston 26 is displaced in right hand direction in the figures under which displacement it carries along the shaft 12 through the axial thrust bearing 22, the grinding disc 28 mounted on said shaft thereunder being carried in a direction towards the grinding disc 34 so as to cause the goods to be ground passing therebetween to be exposed to predetermined grinding pressure. The two grinding discs 28 and 34 rotate in mutually opposite directions.

By connecting the conduits 48, 50 to a pressure source and a drain, respectively, the grinding disc 28 can be displaced in a direction towards, and away of, the grinding disc 34, and further the grinding pressure and therewith the magnitude of the grinding interspace can be varied within suitable limits. The members necessary for this op eration have not been shown because they have no connection with the invention and are known per se.

The axially stationary shaft 14 is with play enclosed by a sleeve-shaped conveyor 52 adjacent the grinding disc 34. The hub 54 of said disc and the disc portion 56 carrying the grinding segments are suitably staggered axially relatively to one another so that the end portion of the conveyor 52 is located radially inside the disc portion 56. The conveyor 52 may have slightly tapering diameter in the direction towards the grinding disc. The casing 36 has on its top side an opening 58 for feeding in of the goods to be ground such as the chips, through a hopper 60 (FIG. 1). The conveyor 52 is in the embodiment according to FIGS. 1-4 on its outside provided with a helical entrainer 62 which projects from the opening 56 under the outer portion of the grinding disc 34. The disc 34 is between its portions 54 and 56 formed with a minor number of spokes 64 in the form of inclined shovels or the like which serve as entrainers for the goods to be ground through the disc to the interspace between the grinding surfaces of the grinding disc. The hub 54 is provided with several projections or teeth 53 spaced over the circumference and having for its object to facilitate the feeding of the goods from the conveyor 52 to the passages formed in the disc 34.

The conveyor 52 has an end portion 66 with slightly greater diameter which on its inner side is slidably mounted on a bracket 68 which is rigidly secured onto the frame 10. Fixed on the external side of the end portion 66 is a toothing rim 70 which through a chain 72 is in driving connection with a toothing rim 73 mounted on a motor 74 which suitably is located in the base part of the frame 10 and the number of revolutions of which is variable. In this way the conveyor 52 can be driven separately with a substantially lower speed than the shafts 12 and 14, respectively. Whereas thus the number of revolutions of the conveyor may be of the order of magnitude of 60 revolutions per minute the shafts are rotated with a speed of the order of magnitude of 1,500 revolutions per minute. This is of essential importance for permitting the feeding of the relatively large chips pieces by means of conveyor 52 and through the passages of the disc 34 without any risk of plug formation 50 that thus the feeding becomes uniform without any interruptions. On the other side, it is important that the grinding discs rotate with great relative speed to become capable of performing the first coarse grinding of the chips.

On both sides of the casing 36 and the conveyor 52 stufiing boxes 76, 78 of known kind are provided. The box 78 is located radially within the end portion 66 of the conveyor.

After the first coarse grinding step the material may be grounded further in at least two steps so as gradually to reach the final condition with separation of fibres and fibre bundles and possibly fibrillation of the individual fibres. The second step also may be effected in a grinding apparatus of the kind described hereinbefore. Alternately for this and also the last grinding step conventional grinding apparatus may be used. The pulp may then be introduced into the apparatus in the form of a liquid suspensron.

The embodiment according to FIGS. 5 and 6 differs from the preceding one by the helical entrainer 62 of the conveyor 52 terminating at a distance from the outlet side of the conveyor where instead inclined vanes 80 are dis posed spaced around the circumference. These vanes serve to advance the chips in a direction to the interspace between the grinding discs.

The grinding operation in the apparatus of the invention may be combined with steam treatment of the vegetable material in any of the treatment steps. The casing 36 may be closed entirely so that a superatmospheric pressure of fluid or vapor may be maintained therein.

While several embodiments of the invention have been shown and described, it is to be understood that this is for the purpose of illustration only, and that the invention is not to be limited thereby, but its scope to be determined by the appended claims.

What we claim is:

1. A grinding apparatus for vegetable material, particularly in relatively large pieces, comprising two grinding discs mounted on shafts and rotatable in relationship to one another and displaceable in axial direction relatively to one another by means of a servo-motor, the goods to be ground being fed between the grinding surfaces of said grinding discs, a rotatable conveyor for feeding the goods between the grinding discs, said conveyor being provided with entrainers, the conveyor adapted to rotate at a substantially lower speed than the rotatable grinding disc and being located in an annular interspace surrounding the shaft of said disc.

2. The grinding apparatus of claim 1 wherein both grinding discs are carried by rotatable shafts, the conveyor concentrically surrounding one of said shafts.

3. The grinding apparatus of claim 2 wherein the conveyor is rotated by a motor separate from the driving motor of the enclosed shaft.

4. The grinding apparatus of claim 3 wherein the grinding disc on the shaft enclosed by the conveyor is provided at the outlet side of the conveyor with annularly distributed flow passages separated from one another by entraining members connecting the hub portion and the outer portion of the disc and destined for the transport of goods to the grinding interspaces between the grinding discs.

5. A grinding apparatus for vegetable material comprising, a pair of grinding discs, each of said discs being borne by a shaft, at least one of the shafts and its disc being rotated, the goods to be ground being fed between the grinding surfaces of the grinding discs, a rotatable conveyor for feeding the goods between the discs, said conveyor being provided with entrainers, said conveyor surrounding one of the shafts and in concentric disposition thereto, and said conveyor adapted to rotate at a lower speed than the speed of rotation of the rotatable grinding disc.

-6. A grinding apparatus for vegetable material comprising, a pair of grinding discs, at least one of said discs being rotated, said rotating disc being carried by a shaft, the goods to be ground being fed between the grinding surfaces of the grinding discs, a rotatable conveyor for feeding the goods between the discs, said conveyor being provided with entrainers, said conveyor surrounding said shaft and in concentric disposition thereto, and said conveyor adapted to rotate at an essentially lower speed than the speed of rotation of the rotatable grinding disc.

I References Cited UNITED STATES PATENTS 976,535 11/1910 Woodcock 24l247 1,123,494 1/1915 Craig 241247 2,751,157 4/1956 Meyer 24167 3,092,338 6/1963 Reinhall 241246 3,215,355 11/1965 Showlin 241-101 3,302,893 2/1967 Feder 24l-37 ROBERT C. RIORDAN, Primary Examiner D. G. KELLY, Assistant Examiner 

